Transcript of "energy sources"

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ENERGY SOURCES CHAPTER 6

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RENEWABLE & NON-RENEWABLE ENERGY SOURCESNON RENEWABLE RENEWABLE The energy sources which  The energy sources when once finished cannot which are either be got again or will take a unlimited or can be got long time to get back back again in a short Fossil fuels like coal, time once finished petroleum, natural gas,  Solar energy, wind wood, dung cakes, nuclear energy (fission) energy, hydro energy, tidal energy, bio-gas, Petroleum will last till 2020 while coal for another geothermal energy, 250 years nuclear energy (fusion)

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RENEWABLE & NON-RENEWABLE ENERGY SOURCESNON RENEWABLE RENEWABLE They cause pollution  They do not cause They should be used pollution judiciously  They are expensive in short run but are cheaper in long run. New research required

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SOLAR ENERGY Thermo nuclear fusion reaction going on in interior of sun release lots of energy This energy radiated by sun in space Earth and planets receive only a small portion Sun releases 3.8 x 1026 joules/sec of heat energy Only 1.7 x 1017 joules/sec reaches Earth which is only 0.000000045792% of total suns energy

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SOLAR ENERGY Radiation from sun reaches in the form of heat and visible light Solar energy reaching the outer surface of atmosphere is called Solar Constant – taken as reference

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SOLAR CONSTANT Average distance between sun and earth is 1.5 x 108 km Solar Constant: The intensity of solar radiation incident on the earth on a unit cross-sectional area, exposed perpendicularly to the rays of the sun at an average distance is termed as Solar constant Its value is: 1.353 KW/m2 Around 47% (0.66kw)of energy that strikes the outer atmosphere will reach the earths surface From the remaining, some is reflected back in space and some absorbed by atmosphere

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SOLAR CONSTANT Most UV rays are eliminated and solar energy reaching earth is in form of heat (infrared radiation) and visible light Land and water absorbs this energy This energy passes through many biological and physical processes

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COMPOSITION OF ENERGY SOURCES Violet light has wave length: 4000A Red light has wave length: 8000A Radiations with wavelength more than that of red color are called Infrared rays Radiations with wavelengths less than that of violet are called Ultraviolet rays X-rays and Gamma rays also have wavelength less than Ultraviolet rays

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COMPOSITION OF ENERGY SOURCES One-third of sunlight passing through atmosphere is in form of Infrared rays (give heat) Rest in form of visible light (violet to red) Infrared rays transmit heat which we feel

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SOLAR APPLIANCES Two categories on basis of working: 1) the solar energy is converted in form of heat. Eg. Solar cooker, solar water heater 2) solar energy is converted into electricity. Eg. Solar cells In 1885, Gunter, an Austrian scientist used a concave mirror in solar boiler In 1876, John Ericson, an American scientist used solar energy to get hot air to run engines.

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SOLAR APPLIANCES We get 0.66 kw solar energy per square metre of earths surface It is very less We need to collect solar energy over large region and for large period Devises should be able to collect and store energy until needed

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SOLAR COOKER Body made of wood, plastic or a fibrous material which is a bad conductor of heat Coated with insulating material on outer surface to prevent loss of heat Plane mirror is fixed on top of box – reflects light into the box Box covered with glass sheet – retains heat inside due to green house effect Inside box – painted black – to absorb heat Cooking vessels (painted black) put inside box

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SOLAR COOKER Temperature ranges from 100 to 140 c when placed for 2-3 hours in sun Used to prepare foods like rice, dal, pulses and vegetables In 1962, India was first country to industrially prepare solar cookers

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SOLAR COOKER - Advantages No fuel required for combustion Maintenance is negligible Pollution free It conserves all the nutrients and vitamins Maintains natural taste of food No personal attention to be given while food being prepared

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SOLAR COOKER - Limitations Food cannot be cooked on cloudy as well as rainy day Takes more time for cooking Cannot do frying, roasting, baking where high and fast heat and cooking required

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SOLAR WATER HEATER Same principle as solar cooker A copper pipe with its outer surface painted black is fixed in form of a coil in a box This increases the surface area for water to heat A reservoir (water tank) kept at a higher level from the ground is used to store cold water, which is connected to a smaller tank slightly above the water heater

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SOLAR WATER HEATER One end of the copper pipe is connected to the bottom of the small tank whose other end is connected halfway between the top and bottom Due to such arrangement, water in the tank repeatedly circulates through copper pipes due to difference of pressure at both ends As water moves through the pipe, it absorbs solar energy, gets heated, and this hot water goes into the tank while cold water replaces it. Hot water being lighter, remains in the upper part of the tank which can be removed by a tap

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SOLAR CONCENTRATORS When a parallel ray of light is focused on a concave mirror, after reflection it is focused on the Principal Focus. Using this fact, solar appliances are made which receive energy from a large area and concentrate into a small area. Such device is called a Solar Concentrator Higher temperature is obtained They can be rotated to face the suns direction

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SOLAR CONCENTRATORS Temperature ranging from 180C – 200C can be obtained Commercial designs use large number of small mirrors fitted together. It brings down the cost Using concentrator kept at height of 50 – 70 metre from ground, water is vapourised and this moves the turbine in generator to generate electricity Such is known as Solar Tower Solar furnace at Mount Louis in France attains temperature of 3000 c and has more than 3500 small mirrors

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WIND ENERGY Modern wind mills are designed to convert Wind energy into Mechanical energy. Modern wind mill – structure similar to large fan – located at a height Necessary parameters: Number of blades, shape and height of windmill. When wind blows the blades rotate, this rotational motion of the blades can be utilised for mechanical work

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WIND ENERGY Number of wind mills erected over a large area is known as Wind Energy Farm In Gujarat, Wind farms located at Lambha near Porbandar, Okha, Mandvi and Dhank Largest wind farm at Kanyakumari in Tamil Nadu which generates 300MW electricity Advantage: Renewable source Limitation: Can be established only where wind speed is high, velocity of wind atleast 16 km/h, cost of installing high, lots of land required, creates noise pollution

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HYDEL ENERGY Energy of flowing water is utilised to produce electricity on large scale by hydro electric power stations High rise dams built to collect water (potential energy) Water from bottom of dam is allowed to flow through turbines (kinetic energy) to produce electricity

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HYDEL ENERGY In Gujarat, Hydroelectric plant of 300 MW capacity of river Tapi at Ukai Also Sardar Sarovar dam on river Narmada Mini or micro hydro electric plants can be constructed in hilly areas where water falls at height of at least 10 metres

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HYDEL ENERGY Advantages: Once plant is installed then needs only maintenance Dam has other uses like irrigation and flood control Limitations: Very costly to instal Large amount of land is lost in the lake thus formed, so forests are destroyed and imbalance is created in nature

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OCEAN THERMAL ENERGY(OTEC) Oceans cover 70% of earths surface During day, water of ocean absorbs very large amount of solar energy Due to this, temperature of water on surface is more while that at depth is less This temperature difference can be used to convert thermal energy into electric energy by Ocean Thermal Energy Conversion Process (OTEC) also known as SRPP (Solar Run Power Plant)

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OCEAN THERMAL ENERGY(OTEC) Temperature difference should be atleast 20C which is available at depth of 700m – 900m Such places found between 20N and 20S latitudes Benefit: energy is available round the clock, whereas in solar energy it is available during the day only

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TIDAL ENERGY Level of water in sea keeps changing near the coast, twice a day This everyday movement of water level is called Tides Energy can be obtained by this rising and falling tides

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TIDAL ENERGY Usually a dam is constructed across a narrow opening of a sea Water moves in and out through the openings and flows over the turbines fixed inside the dams which generate electricity High tides are found only at few places Hence tidal energy not considered as major source of energy

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ENERGY OBTAINED FROM OCEAN WAVES Waves can also be used to generate energy Motion of waves can move turbines kept in their path, thus generating electricity Limitations: They have to be kept far in the sea, thus need lots of maintenance hence not economically cheap

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GEO THERMAL ENERGY Energy obtained from within the earth is called Geothermal energy At certain places the magma in the interior of earth comes up through cracks. It is called Hot spots. It heats the underground water. This water (steam) comes up to surface in form of geysers, it is very hot and can be used to generate electricity Average temperature of hot water geysers is 70C and are found at depth of 800m to 3500m

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GEO THERMAL ENERGY Av. Temperature of steam:150 to 400C Advantages: Most eco-friendly source of energy Cost is half than that of other sources Can be used 24 x 7 throughout the year Is clean (pollution free)

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BIO ENERGY A small fraction of solar energy which reaches the earths surface gets converted into chemical energy by plants during the process of photosynthesis which becomes available in form of Bio-mass Solar energy – photosynthesis – bio mass - energy

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WOOD Main source of energy in most villages Inefficient way to utilise energy source Only 8% to 10% efficiency Smoke formed is harmful to health and polluting Invention of smoke less chulha has helped

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DESTRUCTIVE DISTILLATION OF WOOD Arrange apparatus as shown in figure Put a few pieces of wood in hard glass test tube and water in other Heat the tube containing wood in absence of air Observe: black liquid begins to drip in other test tube containing water and settles at bottom This thick black semifluid is Tar Bring a lighted match stick near the open end. Observe: it starts burning. This is Coal Gas Residue left in test tube is Charcoal Ammonia is also left which is dissolved in water

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BIO GAS Contains 65 to 75% methane, 30 to 40% carbon dioxide and traces of hydrogen, hydrogen sulphide and nitrogen Produced in absence of oxygen during decay of biomass Methane is excellent fuel Calorific value of bio gas: 35 to 40 kJ/gm Traditionally known as Gobar gas as it is made from animal dung, sewage, crop residue

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BIO GAS Two designs of bio-gas plants in India: 1) Fixed dome type 2) Floating dome gas holder type (prepared by Khadi and Village Industry Commission KVIC) Fixed dome type more popular Its dome can by constructed by bricks Has longer life. So economical

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BIO GAS - Working Slurry (semi fluid mixture) of dung, water, waste is prepared in mixing tank Now fed into digestor which is underground tank Biomass decompose into biogas Biogas is used as fuel in industries and also for housing purposes Slurry left behind is good manure Biogas advantages: provides energy, good fertilizer, cleans village, avoids air pollution as no need to burn residue

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HYDROGEN AS FUEL Hydrogen can be used as alternate to traditional fuel It has great potential for future Burning of hydrogen produces large amount of heat and water is by-product It does not cause pollution Still uses are limited. Used in space ships and high temperature flames (welding) Reasons: highly explosive nature, lack of technology at present

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ALCOHOL AS FUEL Good option to traditional sources Manufactured by fermentation of sugar and even other cereal crops Can be mixed with petrol and used as fuel

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COAL Used since centuries First coal mine in India: Raniganj at West Bengal in 1854 Main constituent: carbon Other constituents: hydrogen, oxygen, nitrogen, phosphorus, potassium in compound form Coal burns in air to produce carbon dioxide and large amount of heat is liberated

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COAL Types of coal: Anthracite: 94-98% carbon. Best quality. No ash as residue when burnt Bituminous: 78-87% carbon. Lignite: 28-30% carbon Peat: 27% or less of carbon. Coal is converted into coke by destructive distillation process. Coke is used as a reducing agent in metallurgy, especially for extracting metals from their ores and in making steel

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PETROLEUM Blackish, oily liquid In Greek the word „petro‟ means rock and „oleum‟ means oil Normally formed under sedimentary rocks In 1855 Professor Benjamin proved that crude oil can be used as substitute of coal In 1859 Smith and his two sons dug the first oil well in the world in Pennsylvania in USA In 1867 the first oil well in India was dug at Makkum in Dibrugarh district in Assam. This was first oil well of Asia too

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PETROLEUM Normally obtained at depth of 1500m In india it is found in Assam, Gujarat mainly and in small amounts in Rajasthan, Kashmir, WB, Arunachal pradesh, Tripura and near the banks of Godavari and Krishna rivers In Gujarat: Ankleshwar, Khambat, Navagam, Sanand, Kalol, Jotna, and Bombay High near South Gujarat in the sea 50% of oil comes from Gujarat

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FRACTIONAL DISTILLATION OF PETROLEUM Petroleum purified in Fractional Distillation Tower Tower: 31m high and 3m wide Made of iron. Inner part is lines with specially designed bricks in tray shape, they are porous

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FRACTIONAL DISTILLATION OF PETROLEUM Process: Petroleum is introduced from base of tower at temperature of 400 – 430 c. All hydrocarbons are vaporised Residue of tar and bitumen remains at bottom Hot vapour rises up the tower and product having highest ignition temperature first gets condensed to liquid form Hence main components are seperated

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PETROLEUM GASES Usually contains hydrocarbons like methane, ethane, propane, butane Butane is easily combustible At high pressure it is converted to liquid, filled in cylinders and used in households and industries. It is called Liquified Petroleum Gas (LPG) LPG is highly inflammable. Should be used with care Foul smelling chemical gas Mercapton is added to detect leakage

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PETROLEUM WAX & ASPHALT Petroleum wax: obtained at temperature of more than 400 c. it is semi fluid. Used to prepare candles Tar (Asphalt): the left over residue, thick, black, viscous liquid, called Asphalt (bitumin or tar) is used in the preparation of roads and as water repellent so used in terraces of buildings for water proofing.

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NATURAL GAS Mainly contains Methane Ecofriendly gas. Produces carbon dioxide and water with no hazardous effects on environment India has 100 billion cubic metres of natural gas found in Khambat, Tripura, Jaiselmer, Bombay High and basins of Godavari and Krishna rivers Hydrogen can be extracted to prepare ammonia and urea as artificial fertilizers Dhuvaran power plant in Gujarat runs on gas.

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COMBUSTION OF FUELS Fuel is a source of energy The process in which a substance is burnt in presence of air is termed as Combustion Oxygen is required in this process. Heat and light are produced as it is an Exothermic process

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CONDITIONS FOR BURNING 1) Ignition Temperature The minimum temperature at which a substance starts burning in presence of air is called Ignition temperature A substance does not catch fire if it is heated below its ignition temperature 2) Adequate supply of oxygen Yellow or smoky flame indicates incomplete combustion Blue flame indicates complete combustion 3) Maintaining the minimum level of fuel supply

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HOW TO STOP COMBUSTION If any of the above three conditions are not met, the process of combustion will stop Spray water – increase ignition temperature Cover with sand, carbon dioxide – cut off supply of air Stop the fuel supply

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CHARACTERISTICS OF AN IDEAL FUEL Available easily & in enough quantity Rate of combustion should be higher than room temperature. It should burn completely Should have high calorific value Ignition temperature according to need Minimum amount of non-volatile material Economical Storage and transportation easy and safe Minimum pollution No poisonous gases in combustion

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CALORIFIC VALUE OF FUELS We can find out quality of fuels by knowing how much heat they produce Calorific Value: The heat liberated in joule on complete combustion of 1g of fuel. Unit: kilo joule per gram Hydrogen has highest calorific value Among hydrocarbons – methane has highest value Wood – hydrocarbon – also has oxygen – so burns well due to oxygen – but low calorific value

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EXPERIMENT: TO FIND OUT THE CALORIFIC VALUE OF WAX Let W1 be the weight in gram of candle Take 100 ml water in beaker Note its initial temperature: t1 Ignite the candle, heat the water Note down final temperature: t2 Find out final weight of candle: W2 Calculate rise in temperature: t = t2 – t1 Calculate loss of weight in candle: W = W1 – W2

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EXPERIMENT: TO FIND OUT THE CALORIFIC VALUE OF WAX Mass of water is 100 gms Specific heat of water is 4.186 J/g C Heat absorbed by water: Q = m x s x t By burning 1g of wax candle the heat generated will be Q/W, which is its calorific value

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UNITS OF MASS & ENERGY UNITS OF MASS: In solid state physics or Nuclear Physics the units of mass is considered as Atomic Mass Unit Symbol: u One atomic mass unit is defined as the mass equivalent to 1/12th the mass of unexcited carbon atom of C12 isotope 1 u = 1.66 x 10-27 kg

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UNITS OF MASS & ENERGY UNITS OF ENERGY: In Solid State Physics and Nuclear Physics, “ electron volt” is the unit of energy. It is defined as the change in the energy of an electron when it passes through two points having potential difference 1V Expressed as eV 1 eV = 1.6 x 10-19 joule

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UNITS OF MASS & ENERGY k.eV = kilo electron volt MeV = mega electron volt As per Einsteins theory of Relativity, if „m‟ is the change of mass and E is the energy, relation between m and E is E = mc2 where c is the speed of light in vacuum This shows that mass can be converted into energy and vice versa. Energy obtained from 1 u mass is given by 1 u (mass) = 931.48 MeV (energy)